1. Field of the Invention
The invention relates generally to the field of positioning instrumentation for positioning bodies movable in or horizontal plane and more particularly to electron-beam stage X-Y positioning instrumentation.
2. Brief Description of the Prior Art
Prior electron-beam stage X-Y positioners have generally been of the screw type having a laser interferometer returning position information. There are several problems associated with this type of positioner: first, the manufacture of position screws capable of moving the stage very small fractions of an inch is relatively expensive; second, movement of the stage via such a screw is relatively slow; third, a laser interferometer in the electron beam environment must be placed relatively remote from the stage itself thereby magnifying errors; and fourth, the laser interferometer itself may not possess high compatibility with the high vacuum required in electron-beam etching applications.
The invention described herein contemplates the use of conventional noncontact gage heads to sense the position of the stage by measuring the distance in two dimensions to one of a number of discretely located metal blocks affixed to the bottom of the stage. Noncontact gage heads sense the position of a proximate surface by means of capacitance, magnetism, optics and the like, depending on the type of head employed. Gage heads have heretofore been used in a great variety of applications wherein the distance to a surface is desired to be measured without contact.